1. Field of the Invention
The present invention relates to a solder attach film and a method of forming a solder ball using the same.
2. Description of the Related Art
In general, a semiconductor package protects a semiconductor die from external heat, humidity, and mechanical load, and provides an electrical passage for allowing an electrical signal from the semiconductor die to be transmitted to a main board.
The semiconductor package may include a substrate, a semiconductor die that is adhered to the substrate so as to be electrically connected thereto, an encapsulant for encapsulating the semiconductor die, solder balls that are fused and fixed to the substrate so as to be electrically connected to the main board.
The solder balls are generally formed on the substrate through dotting flux, dropping solder ball, and reflowing solder ball. Dotting the flux is that a predetermined amount of flux that has predetermined viscosity and is volatilized at a high temperature is dotted on electrically conductive pads of the substrate. Dropping the solder ball is that solder balls are dropped on the flux to be temporarily fixed to the flux. Reflowing is that the substrate is put into a high-temperature furnace. Then, the flux is volatilized and removed, and the solder balls are fused to be electrically and mechanically connected to the electrically conductive pads of the substrate.
As described above, in the related art, the solder balls are formed on the substrate by dotting the flux, dropping the solder ball, and reflowing in sequence. Of course, a flux dotting apparatus, a solder ball dropping apparatus, and a reflow apparatus are needed to perform these processes.
Therefore, the related art requires many processes and apparatuses, which causes problems that it takes a lot of time to form the solder balls and a defect rate in a solder ball manufacturing process increases. For example, when the solder ball does not drop at an exact position when dropping the solder ball, solder balls may be doubly formed on one electrically conductive pad, or no solder ball may be formed thereon.
Further, the related art uses expensive solder balls, which causes an increase in a packaging cost. That is, the smaller the diameter of the solder ball, the higher the manufacturing cost of the solder ball. Therefore, in recent years, solder balls having a smaller size need to be used in order to minimize pitches and reduce the size of a chip. Thus, the packaging cost is on an increasing trend.
Of course, as described above, in the related art, the flux dotting apparatus and the solder ball dropping apparatus are necessarily used to form the solder balls, which causes an increase in the initial cost of the apparatuses.